Rotary air lock feeders are widely used today to entrain particulate materials in airstreams. These types of feeders of the prior art are exemplified by those shown in U.S. Pat. Nos. 2,721,767, 3,556,355 and 4,268,205 and in Canadian Pat. No. 560,263. Today, they typically have a metering chamber in which a multi-vaned rotor is rotatably driven about a horizontal axis. A hopper is mounted above the chamber through which materials may be gravity or force fed down into the top of the metering chamber. A discharge shoot is provided in the bottom of the chamber through which the material is discharged after having been metered by the rotor. Material exiting the chamber through the discharge shoot is delivered into an air duct through which a stream of air flows and thereby becomes entrained in the airstream.
With some of the more recent types of rotary air lock feeders the airstream is passed through a lower portion of the metering chamber itself, fed through aligned inlet and outlet ports in the chamber end walls. These are exemplified in U.S. Pat. Nos. 3,009,744, 4,111,493 and 4,465,239.
When used to entrain fibrous insulation into airstreams to form layers or beds of insulation in situ, rotary air lock feeders of the prior art have had several definitive problems associated with their use. Specifically, the length of the feeders and associated hoppers, as measured in the direction of air flow, has been limited. Where made relatively long, such as in excess of some 30 inches to increase capacity, and thus delivery rate, they have tended to become jammed or clogged as gravity empties the longer airlocks too quickly for the airstreams to move the material. In addition, even rotary air lock feeders of lesser lengths have tended to create uneven, pulsating streams of insulation. Thus, streams of insulation delivered from rotary air lock feeders of the prior art have been uneven, pulsating, limited in material flow rates and susceptible to becoming jammed and clogged.
Accordingly, it is to the provision of a rotary air lock feeder and method of feeding particulate materials such as fibrous insulation, that overcomes these limitations of the prior art, to which the present invention is primarily directed.